I'm on Ubuntu 21.10. I use gnome-flashback with Compiz. gnome-panel (version: 3.41.2) keeps crashing for me for some reason. Here's a log file but I can't seem to find what the problem is.
Gtk-Message: 14:07:17.772: Failed to load module "xapp-gtk3-module"
(gnome-panel:202571): indicator-applet-WARNING **: 14:07:17.936: Binding '<Super>F1' failed!
(gnome-panel:202571): indicator-applet-WARNING **: 14:07:17.937: Binding '<Super>F1' failed!
(gnome-panel:202571): indicator-applet-WARNING **: 14:07:17.938: Binding '<Super>F1' failed!
(gnome-panel:202571): indicator-applet-WARNING **: 14:07:17.964: Binding '<Super>S' failed!
(gnome-panel:202571): Indicator-Appmenu-CRITICAL **: 14:07:18.369: Unable to register the object to DBus: An object is already exported for the interface com.canonical.AppMenu.Registrar at /com/canonical/AppMenu/Registrar
(gnome-panel:202571): Indicator-Appmenu-CRITICAL **: 14:07:18.369: Unable to register the object to DBus: An object is already exported for the interface com.canonical.AppMenu.Registrar at /com/canonical/AppMenu/Registrar
(gnome-panel:202571): Indicator-Appmenu-CRITICAL **: 14:07:18.464: Unable to claim the name com.canonical.AppMenu.Registrar
(gnome-panel:202571): Indicator-Appmenu-CRITICAL **: 14:07:18.464: Unable to claim the name com.canonical.AppMenu.Registrar
(gnome-panel:202571): GLib-GObject-WARNING **: 14:07:24.041: invalid unclassed pointer in cast to 'GtkWidget'
(gnome-panel:202571): Gtk-CRITICAL **: 14:07:24.041: gtk_widget_set_sensitive: assertion 'GTK_IS_WIDGET (widget)' failed
...
(gnome-panel:202571): Gtk-CRITICAL **: 14:07:26.503: gtk_window_set_attached_to: assertion 'GTK_IS_WINDOW (window)' failed
(gnome-panel:202571): GLib-GObject-WARNING **: 14:07:26.503: invalid (NULL) pointer instance
(gnome-panel:202571): GLib-GObject-CRITICAL **: 14:07:26.504: g_signal_connect_data: assertion 'G_TYPE_CHECK_INSTANCE (instance)' failed
(gnome-panel:202571): Gtk-CRITICAL **: 14:07:26.504: gtk_window_set_screen: assertion 'GTK_IS_WINDOW (window)' failed
(gnome-panel:202571): GLib-GObject-WARNING **: 14:07:26.707: invalid unclassed pointer in cast to 'GtkWidget'
...
(gnome-panel:202571): GLib-GObject-WARNING **: 14:10:04.942: invalid unclassed pointer in cast to 'GtkWidget'
(gnome-panel:202571): Gtk-CRITICAL **: 14:10:04.942: gtk_widget_set_sensitive: assertion 'GTK_IS_WIDGET (widget)' failed
(gnome-panel:202571): Gtk-WARNING **: 14:11:06.528: ../../../../gtk/gtkwidget.c:6776: no accelerator (115,4) installed in accel group (0x55c819556660) for Genericmenuitem (0x55c819b549a0)
(gnome-panel:202571): Gtk-WARNING **: 14:11:06.528: ../../../../gtk/gtkwidget.c:6776: no accelerator (112,4) installed in accel group (0x55c819556660) for Genericmenuitem (0x55c819b54d80)
(gnome-panel:202571): Gtk-WARNING **: 14:11:06.528: ../../../../gtk/gtkwidget.c:6776: no accelerator (120,4) installed in accel group (0x55c819556660) for Genericmenuitem (0x55c819b5a1d0)
(gnome-panel:202571): Gtk-WARNING **: 14:11:06.528: ../../../../gtk/gtkwidget.c:6776: no accelerator (99,4) installed in accel group (0x55c819556660) for Genericmenuitem (0x55c819b5a5b0)
(gnome-panel:202571): Gtk-WARNING **: 14:11:06.528: ../../../../gtk/gtkwidget.c:6776: no accelerator (118,4) installed in accel group (0x55c819556660) for Genericmenuitem (0x55c819b5a990)
(gnome-panel:202571): Gtk-WARNING **: 14:11:06.528: ../../../../gtk/gtkwidget.c:6776: no accelerator (102,4) installed in accel group (0x55c819556660) for Genericmenuitem (0x55c819b5ad70)
(gnome-panel:202571): Gtk-WARNING **: 14:11:06.529: ../../../../gtk/gtkwidget.c:6776: no accelerator (104,4) installed in accel group (0x55c819556660) for Genericmenuitem (0x55c819b815b0)
(gnome-panel:202571): Gtk-WARNING **: 14:11:06.529: ../../../../gtk/gtkwidget.c:6776: no accelerator (117,4) installed in accel group (0x55c819556660) for Genericmenuitem (0x55c819b88d80)
(gnome-panel:202571): GLib-GObject-WARNING **: 14:11:06.613: invalid unclassed pointer in cast to 'GtkWidget'
...
(gnome-panel:202571): GLib-GObject-WARNING **: 14:11:07.160: invalid unclassed pointer in cast to 'GtkWidget'
(gnome-panel:202571): Gtk-CRITICAL **: 14:11:07.160: gtk_widget_set_sensitive: assertion 'GTK_IS_WIDGET (widget)' failed
(gnome-panel:202571): Indicator-Appmenu-CRITICAL **: 14:11:07.232: menus_destroyed: assertion 'IS_WINDOW_MENU(wm)' failed
(gnome-panel:202571): Indicator-Appmenu-CRITICAL **: 14:11:07.232: menus_destroyed: assertion 'IS_WINDOW_MENU(wm)' failed
(gnome-panel:202571): Indicator-Appmenu-CRITICAL **: 14:11:07.232: menus_destroyed: assertion 'IS_WINDOW_MENU(wm)' failed
(gnome-panel:202571): GLib-GObject-WARNING **: 14:11:08.079: invalid unclassed pointer in cast to 'GtkWidget'
(gnome-panel:202571): Gtk-CRITICAL **: 14:11:08.079: gtk_widget_set_sensitive: assertion 'GTK_IS_WIDGET (widget)' failed
...
(gnome-panel:202571): Gtk-CRITICAL **: 14:14:37.169: gtk_widget_set_sensitive: assertion 'GTK_IS_WIDGET (widget)' failed
(gnome-panel:202571): GLib-GObject-WARNING **: 14:14:37.228: invalid unclassed pointer in cast to 'GtkWidget'
(gnome-panel:202571): Gtk-CRITICAL **: 14:14:37.228: gtk_widget_set_sensitive: assertion 'GTK_IS_WIDGET (widget)' failed